1. Field of the Invention
The present invention relates to a new manufacturing method for vibration proof rubber that is formed by compounding rubber elastic bodies between inner metal fittings and outer shell metal fittings.
2. Prior Art
Conventionally, when vibration proof rubber (a rubber vibration insulator) obtained by compounding rubber elastic bodies between an inner metal fitting and an outer shell metal fitting, such as cylindrical vibration proof rubber, is manufactured, curing adhesion of the rubber elastic body between the inner metal fittings and auxiliary outer cylinder metal fittings is performed first and then, the outer shell metal fitting part is fitted thereto by further performing drawing. This is the method generally utilized. In other types of methods, curing adhesion of the rubber elastic body to the inner cylinder (tubal) metal fitting is first performed and then, after press fitting it to the outer shell fitting, adhering is performed by heating. In yet another method, adhesives are applied to the inner surface of the outer cylinder metal fitting and by cure bonding the rubber elastic body is adhered to the outer cylinder metal fitting. Then after press fitting the inner cylinder metal fitting, with adhesives on the outer surface, into a hole in the rubber elastic body, adhesion using heat is performed (as in U.S. Pat. No. 2,572,215).
However, because the compressibility of the rubber is low in the former method, it is difficult to sufficiently remove the contractive distortion of the rubber, and the durability is poor. In addition, an auxiliary outer cylinder metal fitting is required.
In the latter method, although sufficient preliminary compression can be given to the elastic body, there is a defect in that adhesion between the rubber and the metal is not strong enough.
Recently, for the purpose of alleviating such defect, it has been the practice to treat the bonding area of the rubber elastic body with halogenation. However, due to the halogen component used for the pre-bonding treatment, the bonded base surface of the outer shell metal fitting becomes corroded. Accordingly, this method also cause a bonding defect over a long period of use.